Enhanced Oil Recovery (abbreviated EOR) refers to techniques for increasing the amount of unrefined petroleum, or crude oil that may be extracted from an oil reservoir (e.g. an oil field). Using EOR, 40-60% of the reservoir's original oil can typically be extracted compared with only 20-40% using primary and secondary recovery (e.g. by water injection or natural gas injection). Enhanced oil recovery may also be referred to as improved oil recovery or tertiary recovery (as opposed to primary and secondary recovery).
Enhanced oil recovery may be achieved by a variety of methods including miscible gas injection (which includes carbon dioxide flooding), chemical injection (which includes polymer flooding, alkaline flooding and surfactant flooding), microbial injection, or thermal recovery (which includes cyclic steam, steam flooding, and fire flooding). The injection of various chemicals, usually as dilute aqueous solutions, has been used to improve oil recovery. Injection of alkaline or caustic solutions into reservoirs with oil that has organic acids naturally occurring in the oil will result in the production of soap that may lower the interfacial tension enough to increase production. Injection of a dilute solution of a water soluble polymer to increase the viscosity of the injected water can increase the amount of oil recovered in some formations. Dilute solutions of surfactants such as petroleum sulfonates may be injected to lower the interfacial tension or capillary pressure that impedes oil droplets from moving through a reservoir. Special formulations of oil, water and surfactant microemulsions have also proven useful. Application of these methods is usually limited by the cost of the chemicals and their adsorption and loss onto the rock of the oil containing formation.
Some unrefined petroleum contains carboxylic acids having, for example, C11 to C20 alkyl chains, including napthenic acid mixtures. The recovery of such “reactive” oils may be performed using alkali (e.g. NaOH or Na2CO3) in a surfactant composition. The alkali reacts with the acid in the reactive oil to form soap. These soaps serve as an additional source of surfactants enabling the use of much lower level of surfactants initially added to affect enhanced oil recovery (EOR). However, when the available water supply is hard, the added alkali causes precipitation of cations, such as Ca+2 or Mg+2. In order to prevent such precipitation an expensive chelant such as EDTA may be required in the surfactant composition. Alternatively, expensive water softening processes may be used.
The quaternary ammonium surfactant compositions provided herein address these and other needs in the art. Embodiments of the quaternary ammonium compounds represent a cost effective alternative to commonly used EOR surfactants (e.g. surfactants derived from Guerbet alcohols). The compounds described herein may improve the water wettability of the surface material in a well therefore increasing the efficiency of oil production. The compounds provided herein may further have a stabilizing effect on the foam and therefore the foam level. For instance, in the presence of a compound disclosed herein the stability of foam pumped into the well during the process of oil recovery may be increased when compared to the absence of the compound. In some embodiments, the compounds provided herein may decrease the water drainage from the surface of the bubble. In some embodiments, the level of foam pumped into the well may increase in the presence of the compound provided herein. In some embodiments, the compounds described herein may improve the effectiveness of co-surfactants (e.g. alkoxy carboxylates, alkoxy sulfates, sulfonate compounds such as ABS or IOS) to a surprising degree. In some embodiments, where the sulfonate compounds are combined with the compounds provided herein, the combination may be more stable and effective when compared to the stability and effectiveness of the sulfonate compounds in the absence of the compounds provided herein.